Dynamically Tunable Asymmetric Transmission in PT-Symmetric Phase Gradient Metasurface

Tapar, Jinal and Kishen, Saurabh and Emani, Naresh Kumar (2021) Dynamically Tunable Asymmetric Transmission in PT-Symmetric Phase Gradient Metasurface. ACS Photonics, 8 (11). pp. 3315-3322. ISSN 2330-4022

Text
ACS_Photonics.pdf - Published Version
Restricted to Registered users only
Download (5MB) | Request a copy

Abstract

Active optical metasurfaces have attracted significant research attention in recent times. The conventional thermal and free-carrier induced index-tuning mechanisms have been widely explored to realize dynamic modulation of the optical properties. However, their modulation efficiency is limited by the intrinsic response of functional materials. The recent advances in the concept of PT (parity-time) symmetry and spatiotemporal modulation of permittivity have opened new avenues to realize dynamic tunability. In this work, we propose an all-dielectric PT-symmetric metasurface to tune the intensity and angular response of light through dynamic gain-loss modulation. Our approach shows tunable asymmetric transmission in a vertically stacked Ga0.5In0.5P phased-array metasurface. The overall metasurface is optimized for operation at a wavelength of 655 nm (typical PL emission peak of Ga0.5In0.5P). The transmission is predominantly in the zeroth diffraction order (η0 ∼0.80, η1 ∼0.18) for loss side normal incidence, and an amplified transmission is observed in the first diffraction order (η0 ∼0.04, η1 ∼0.79) for gain side incidence. In addition to the asymmetric transmission for normal incidence, the proposed metasurface also exhibits asymmetric amplification in transmission for oblique incidence. An optimal arrangement of gain-loss resonators combined with tunable pumping (either optical or electrical) can pave the way toward on-chip reconfigurable nanophotonic devices. ©

[error in script]

IITH Creators: